How to choose a vacuum pump？

Recommendations for vacuum pump selection:

1. The selected vacuum pump must be able to extract the gas released during the process.

2. The ultimate vacuum degree of the selected main pump must be higher than the vacuum degree required by the pumped container.

3. The pumping speed of the selected main pump must be greater than the maximum air release in the process.

4. The working medium of the selected vacuum pump and the materials for making the pump must meet the technological requirements.

5. For the continuous production process, the selected vacuum pump must reliably meet the needs of continuous production.

The method of vacuum pump selection:

1. The vacuum degree required by the process

The working pressure of the vacuum pump should meet the working pressure requirements of the process, and the vacuum degree should be higher than half to one order of magnitude higher than the vacuum degree of the vacuum equipment. (For example, the vacuum process requires a vacuum degree of 100pa (absolute pressure), and the vacuum degree of the vacuum pump should be at least 50pa-10pa). Generally, if the absolute pressure is required to be higher than 3300Pa, the water ring vacuum pump is preferred as the vacuum device. If the absolute pressure requirement is lower than 3300Pa, the water ring vacuum pump cannot be selected, and the rotary vane vacuum pump or a vacuum pump with a higher vacuum level is selected.

2. The amount of pumping required by the process (the pumping rate)

The vacuum pump requires the pumping rate (that is, the ability of the vacuum pump to discharge gas, liquid, and solid under its working pressure), the general unit: m3/h, L/S, m3/min. The specific calculation method can refer to the following formula to calculate and select by yourself. Of course, the selection of vacuum pumps is a comprehensive process, involving factors such as relevant experience.

The formula for calculating the pumping rate:

S=2.303（V/t）Log(P1/P2)

S is the pumping rate of the vacuum pump (L/s)

V is the vacuum chamber volume (L) (m3)

t is the time required to reach the required vacuum degree (s) (h)

P1 is the initial vacuum degree (Torr) (pa)

P2 is the required degree of vacuum (Torr) (pa)

E.g:

V=500L

t=30s

P1=760Torr

P2=50Torr

Then: S=2.303V/t Log(P1/P2)

=2.303x500/30xLog(760/50)

=45.4L/s(163.4m3/h)

Of course, the above formula is only the theoretical calculation result, and there are several variable factors that have not been taken into account, such as pipeline flow resistance, leakage, the flow resistance of the filter, the temperature of the gas being pumped, etc. In practice, the safety factor should also be taken into account.

3. Determine the composition of the extracted object

4. Does the pumped object pollute the rubber or oil? 

Corresponding vacuum equipment should be selected for different pumped media. If the gas contains a large amount of steam, particles, and corrosive gases, it should be considered in the inlet pipe of the pump to install corresponding equipment on the pipeline, such as condensers, filters, etc.

5. Does the noise, vibration, and aesthetics of the vacuum pump affected?

6. When purchasing vacuum pumps and vacuum equipment, the quality of the equipment, transportation, and repair and maintenance costs should also be prioritized.